1. Field of the Invention
The present invention relates to methods of separating diastereomeric isomers, and more particularly to the separation of isomers of diastereomeric alcohols.
2. Brief Description of the Prior Art
Isomers of diastereomeric alcohols are separable by a number of techniques such as by fractional distillation, crystallization, crystallization of derivatives such as hydrogen phthalates or para-nitro benzoates, and chromatography. The particular method of separation to be employed is generally chosen on the basis of cost and separation efficiency.
Distillation is often the preferred separative technique. It is usually an efficient, less costly, and less labor intensive process that is more easily adaptable to large scale production, in comparison with other techniques. However, distillation has not been a viable option for the separation of a number of isomers of diastereomeric alcohols, in particular those isomers where the alcohols have boiling points that are very close to each other. In such instances, resort must be made to crystallization, chromatography or other techniques, with their higher cost and other associated disadvantages. The latter is the case with the isomeric pair alpha-fenchol and beta-fenchol, which have a boiling point difference of only 0.3.degree. C.
Efficient and cost effective separative techniques for such closely boiling alcohol isomers are needed. The present invention is directed to this important end.